Thermal conversion products comprised of maleic anhydride and oligoalkenes, derivatives of the thermal conversion products with amines or alcohols and the use thereof

ABSTRACT

Thermal reaction products of maleic anhydride and oligoalkenes are obtainable by oligomerization of linear C 8 - to C 12 -1-alkenes, preferably in the presence of a titanium, zirconium or hafnium metallocene catalyst and of an activator based on organoaluminum, organoboron or carbocationic compounds and have a vinylidene double bond content of more than 30% and have a number average molecular weight from 1000 to 20,000. 
     Derivatives thereof with amines or alcohols are used as fuel additives and lubricant additives.

This application is a 377 of PCT/EP99/01253 Feb. 26, 1999.

Thermal reaction products of maleic anhydride and oligoalkenes,derivatives of the thermal reaction products with amines or alcohols anduse of these derivatives as fuel additives and lubricant additives

The present invention relates to thermal reaction products of maleicanhydride and oligoalkenes obtained from specific linear α-olefins,which have a number average molecular weight of from 700 to 20,000, anda process for the preparation of these thermal reaction products. Thepresent invention furthermore relates to derivatives of the thermalreaction products with amines or alcohols in the form of thecorresponding alkenylsuccinamides, alkenylsuccinimides oralkenylsuccinic esters and the use of these derivatives as fueladditives and lubricant additives. The present invention also relates tomotor oils which contain these derivatives as additives.

Imides of polyisobutenylsuccinic acids have long been known as ashlessdispersants in the form of alkenylsuccinic acid derivatives. However,the polyisobutenyl radical and also other corresponding long-chainradicals known from the prior art do not yet ensure an optimum propertyspectrum of such dispersants. In particular, viscosity behavior is stillunsatisfactory, i.e. a reduction in the low-temperature viscosity isdesired.

WO-A 93/24539 (1) discloses poly-1-olefins obtained from C₃- toC₂₀-1-olefins, such as propene, 1-butene, 1-pentene or 1-hexene, havinga number average molecular weight of from 300 to 10,000, which areprepared by conventional metallocene catalysis. Said 1-olefins arealways used as a mixture with more readily volatile saturated andunsaturated hydrocarbons; for example, an industrial butane/butenestream or industrial isobutene-containing butene stream (“refinedproduct I/II” from the steam cracker) is used. The poly-1-olefinsobtained can then be converted by means of maleic anhydride intofunctionalized products which are used, inter alia, for lubricating oilsand as fuel additives.

WO-A 96/28486 (2) relates to copolymers of unsaturated carboxylic acidsor their anhydrides and oligomers of 1-olefins of 3 to 14 carbon atoms,which can be prepared by metallocene catalysis. Inter alia, n-decene isalso mentioned here as a 1-olefin. The average molecular weight of theolefin oligomers is from 300 to 10,000. The copolymers obtained from theunsaturated dicarboxylic acids (anhydrides) and the olefin oligomers aresuitable, after derivatization with amines, as fuel additives andlubricant additives.

WO-A 96/23751 (3) discloses olefin oligomers which are prepared by meansof metallocene catalyst systems and are based on linear and cyclic C₂-to C₁₂-olefins, e.g. 1-decene. Their weight average molecular weight({overscore (M)}_(w)) is from 100 to 20,000, with a molecular weightdistribution {overscore (M)}_(w)/{overscore (M)}_(n) (weight averagevalue/number average value) of from 1.0 to 2.4. Their degree ofpolymerization is from 2 to 200. These olefin oligomers can be furtherprocessed according to (3) by the conventional chemical reactions, suchas hydroformylation and/or hydroamination, to give functionalizedcompounds which are suitable, for example, as fuel additives orlubricant additives.

It is an object of the present invention to remedy the deficiencies ofthe prior art.

We have found that this object is achieved by thermal reaction productsof maleic anhydride and oligoalkenes which are obtainable byoligomerization of linear C₈- to C₁₂-1-alkenes, have a vinylidene doublebond content of more than 30%, in particular more than 50%, especiallymore than 60%, and have a number average molecular weight of from 700 to20,000.

Suitable linear C₈- to C₁₂-1-alkenes and mixtures thereof are 1-octene,1-nonene, 1-decene, 1-undecene and 1-dodecene and mixtures thereof. In apreferred embodiment, oligoalkenes which are obtainable bymetallocene-catalyzed oligomerization of linear 1-decene are used, itbeing possible for up to 40 mol %, based on the amount of linear1-decene, of further linear C₈- to C₁₂-1-alkene to be incorporated aspolymerized units.

The essential monomer component in this preferred embodiment is thuslinear 1-decene, which may be oligomerized alone or as a mixture with upto 40, in particular up to 20, especially up to 5, mol %, based on theamount of 1-decene, of further linear C₈- to C₁₂-1-alkenes (1-octene,1-nonene, 1-undecene and/or 1-dodecene).

Said 1-alkene can be used in chemically pure form (purities of, usually,from 99 to 99.9% by weight) or as industrial mixtures in purities of,usually, from 90 to 99% by weight, the remaining components in theindustrial mixtures usually being roughly equally volatile,polymerizable or unpolymerizable components (for example unsaturatedisomers, homologs or saturated hydrocarbons). As a rule, the 1-alkenesused are virtually free of more highly volatile components, especiallyfree of more highly volatile saturated or unsaturated hydrocarbons, inparticular those having less than 8 carbon atoms; virtually free meansthat at most less than 1, in particular less than 0.5, % by weight ofsuch more highly volatile components may occur.

In the oligomerization of said linear C₈- to C₁₂-1-alkenes, theprocedure is carried out in particular under metallocene catalyst,especially in the presence of a titanium, zirconium or hafniummetallocene catalyst and of an activator based on organoaluminum,organoboron or carbocationic compounds.

The systems used for the oligomerization and comprising metallocenecatalyst and activator are conventional catalyst systems. By varying thestructure of the metallocene, it is possible to adjust the desiredmolecular weight ranges of the oligoalkenes in a known manner. Theoligomerization is carried out as a rule in a suitable medium (reactionmixture), for example an organic solvent, under the conditions usual forthis purpose.

The catalyst systems do not have to meet any special requirement, apartfrom being substantially soluble in the reaction mixture. The reactionmixture is the mixture which is present in the time after thecombination of all reaction components up to, at the latest, thedestruction of the catalyst system after the end of the oligomerizationreaction. The solubility of the catalyst system in the reaction mixtureis determined by measuring the turbidity of the reaction mixtureanalogously to DIN 38404. Substantial solubility of the catalyst systemis present if the turbidity number is from 1 to 10, preferably from 1 to3.

The metallocene component of the catalyst system is a complex oftitanium, of zirconium or of hafnium, in which the metal atom M isbonded, in the form of a sandwich, between two unsubstituted orsubstituted cyclopentadienyl groups, the remaining valences of thecentral atom M being saturated by readily exchangeable leaving atoms orleaving groups X¹, X².

Suitable metallocene complexes are those of the formula Cp₂MX¹X², whereM is titanium, zirconium or hafnium, preferably zirconium.

CP₂ is a pair of unsubstituted or substituted cyclopentadienyl ligands.Here, both cyclopentadienyl ligands or only one of the two may besubstituted.

Where the substituents are C₅- to C₃₀-alkyl, the cyclopentadienyl ringsare usually symmetrically substituted. This means that the type andnumber as well as the position of the alkyl substituents of one Cp ringare identical to the type, number and position of the alkyl substituentsof the second Cp ring. The number of alkyl groups of thecyclopentadienyl ring is from 1 to 4.

Suitable C₅- to C₃₀-alkyl radicals are the aliphatic radicals pentyl,hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl,tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl andeicosyl and their isomers, for example neopentyl and isooctyl, and thecycloaliphatic radicals cyclopentyl and cyclohexyl. n-Octadecyl isparticularly suitable.

The unsubstituted or C₅- to C₃₀-alkyl-substituted cyclopentadienyl unitsmay however also be substituted by 1 or 2 C₄- to C₁₀-alkyl units eachwhich, together with the cyclopentadienyl unit, form a fused ringsystem, such as the tetrahydroindenyl system.

However, other suitable substituted cyclopentadienyl ligands are thosepairs in which at least one cyclopentadienyl unit is substituted by atleast one organosilyl group —Si(R¹)₃. R¹ is then an organic group of 1to 30 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl,isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, hexyl,heptyl, octyl, nonyl, cyclohexyl, phenyl or p-tolyl. Preferredorganosilyl radicals are trimethylsilyl and tert-butyldimethylsilyl, inparticular trimethylsilyl.

In the case of organosilyl substitution on the cyclopentadienyl unitsthe symmetrical substitution pattern is not absolutely essential but isalso not ruled out.

Those metallocene catalysts in which both cyclopentadienyl ligands arelinked to one another by means of a bridge member are also of interest.Such bridge members generally have 1 to 4 atoms (carbon atoms and/orheteroatoms, such as Si, N, P, O, S, Se or B) and may have alkyl sidechains, e.g. 1,2-ethylidene, 1,3-propylidene or dialkylsilane bridges.

Examples of readily exchangeable, formally negatively charged leavingatoms or leaving groups X¹, X² of the metallocene complexes of theformula Cp₂MX¹X² are hydrogen and halogen, such as fluorine, bromine,iodine and preferably chlorine. Other examples are alcoholates, such asmethanolate, ethanolate, n-propanolate, isopropanolate, phenolate,trifluoro-methylphenolate, naphtholate and silanolate.

Other preferred groups X¹, X² are in particular C₁- to C₁₀-alkylradicals, especially methyl, ethyl, propyl, isopropyl, butyl, isobutyl,sec-butyl, tert-butyl, pentyl, neo-pentyl and hexyl, preferably methyl,tert-butyl and neo-pentyl, and furthermore alicyclic C₃ toC₁₂-hydrocarbon radicals, such as cyclopropyl, cyclobutyl, cyclopentyland in particular cyclohexyl, or C₅- to C₂₀-bicycloalkyl, such asbicyclopentyl and in particular bicycloheptyl and bicyclooctyl.

Examples of substituents X¹, X² having aromatic structural units are C₆-to C₁₅-aryl, preferably phenyl or naphthyl, alkylaryl or arylalkyl, eachhaving 1 to 10 carbon atoms in the alkyl radical and 6 to 20 carbonatoms in the aryl radical, for example tolyl and benzyl.

Individual examples of suitable metallocene complexes are:bis(n-octadecylcyclopentadienyl)zirconium dichloride,bis(trimethylsilylcyclopentadienyl)zirconium dichloride,bis(tetrahydroindenyl)zirconium dichloride,bis[(tert-butyldimethylsilyl)cyclopentadienyl]zirconium, dichloride,bis(di-tert-butylcyclopentadienyl)zirconium, dichloride,(ethylidenebisindenyl)zirconium dichloride,[ethylidenebis(tetrahydroindenyl)]zirconium dichloride and bis[3,3-(2-methylbenzindenyl)]dimethylsilanediylzirconium dichloride.

Said metallocene complexes can be synthesized in a simple manner byknown processes, e.g. Brauer (editor): Handbuch der PräparativenAnorganischen Chemie, Volume 2, 3^(rd) edition, pages 1395 to 1397,Enke, Stuttgart 1978. A preferred process starts from the lithium saltsof the correspondingly substituted cyclopentadienyls, which are reactedwith the transition metal halides.

Expediently, only one metallocene complex is used in the oligomerizationreaction, but it is also possible to use mixtures of differentmetallocene complexes.

In addition to the metallocene complexes, the catalyst systems alsocontain activators which are known per se and are also referred to ascocatalysts in the literature. In general, they alkylate the transitionmetal component of the catalyst system and/or abstract a ligand X fromthe transition metal component, so that finally a catalyst system forthe oligomerization of olefinically unsaturated hydrocarbons can form.In general, organometallic compounds of the 1^(st) to 3^(rd) main groupsor the 2^(nd) subgroup of the Periodic Table are suitable for achievingthis object, but other acceptor compounds, for example carbocationicsalts, can also be used.

Activator compounds suitable in the present case are, in addition toaluminum fluoride, in particular organoaluminum and organoboroncompounds and carbocationic salts. Open-chain or cyclic oligomericaluminoxane compounds which can be obtained by reactingtrialkylaluminums, in particular trimethyl- or triethylaluminum, withwater are preferred.

Suitable cocatalysts are in general also aluminum organyls of theformula Al(R²)₃, where R² is hydrogen or C₁- to C₁₀-alkyl, preferablyC₁- to C₄-alkyl, in particular methyl, ethyl or butyl. R² mayfurthermore be arylalkyl or alkylaryl, each having 1 to 10 carbon atomsin the alkyl radical and 6 to 20 carbon atoms in the aryl radical.

Other suitable alkylaluminums Al(R²)₃ are those in which R², in additionto the abovementioned radicals, may also be fluorine, chlorine, bromineor iodine, with the proviso that at least one radical R² is an organiccarbon radical or a hydrogen atom. Particularly preferred compounds aretrimethylaluminum, triethylaluminum, triisobutylaluminum,diisobutylaluminum hydride and diethylaluminum chloride.

Other suitable activators are organoboron compounds, for exampletrisarylboron compounds, preferably tris(pentafluorophenyl)boron, andfurthermore salts of carbonium ions, preferably triphenylmethyltetraarylborate, in particular triphenylmethyltetra(pentafluorophenyl)borate.

Said Al, B or C compounds are known or are obtainable in a manner knownper se.

The activators can be used alone or as mixtures in the catalyst system.

The activator component is preferably used in a molar excess relative tothe metallocene complex. The molar ratio of activator to metallocenecomplex is in general from 100:1 to 10,000:1, preferably from 100:1 to1000:1.

The components of the catalyst systems described can be introduced intothe oligomerization reactor individually in any desired sequence or as amixture. The metallocene complex is preferably mixed with at least oneactivator component before entering the reactor, i.e. is preactivated.

The preparation of the oligoalkenes can be carried out either batchwiseor preferably continuously in the conventional reactors used for theoligomerization of olefins. Suitable reactors include continuouslyoperated stirred kettles, it also being possible, if required, to use aplurality of stirred kettles connected in series.

The oligomerization can be carried out in a suspension, in liquidmonomers and in inert solvents. In the oligomerization in solvents, inparticular liquid organic hydrocarbons, such as benzene, ethylbenzene ortoluene, are used. The oligomerizations are preferably carried out in areaction mixture in which the liquid monomer is pre sent in excess .

Since the oligomerization is carried out as a rule at from −20° C. to200° C., in particular from 0 to 140° C., especially from 30° C. to 110°C., it can generally be effected by the low-pressure or medium-pressureprocess. The amount of catalyst used is not critical.

The oligoalkenes prepared by metallocene catalysis contain unsaturateddouble bonds, owing to the oligomerization mechanism; here, theproportion of terminal vinylidene double bond is particularly high, andit is this that permits the substantially complete thermal reaction withmaleic anhydride.

The oligoalkenes described have a number average molecular weight({overscore (M)}_(n)) of from 700 to 20,000, preferably from 1000 to18,000, especially from 2000 to 15,000, in particular from 3000 to12,000. The number average molecular weight is usually determined by gelpermeation chromatography (GPC).

The molecular weight distribution {overscore (M)}_(w)/{overscore(M)}_(n) (weight average value/number average value) is in general from1.5 to 5, it being possible for a narrow distribution to be achieved forexample by extraction of samples having a broad distribution, and for abroad distribution to be obtained also by mixing. If uniform catalystsystems are used, the distribution is in general from 1.8 to 3.0. Incertain circumstances, a broader distribution may be more advantageous;in particular , a broad low molecular weight flank in the distributioncan improve the dispersing effect of the end products. Furthermore,bimodal distributions produced by mixing may also have an advantageouseffect.

The oligoalkenes described are reacted with maleic anhydride (MAA) byconventional thermal ene reaction to give alkenyl-succinic anhydrides,which as a rule carry 1 or 2 succinic anhydride units per alkenyl chain.For this purpose, the maleic anhydride and the oligoalkenes areexpediently heated to temperatures of from 150 to 250° C. , preferablyfrom 170 to 220° C., in the absence of compounds initiating free radicalchain reactions. The reaction is advantageously carried out under inertgas (e.g. nitrogen).

The novel thermal reaction products of maleic anhydride and oligoalkenescan be converted by means of amines or alcohols, by conventionalmethods, into the corresponding alkenylsuccinamides, alkenylsuccinimidesor alkenylsuccinic esters; the present invention likewise relates tosuch derivatives.

In particular polyols, especially aliphatic polyhydroxy compounds having2 to 6 hydroxyl groups, may be used here as alcohols. Examples of diolsare ethylene glycol, 1,2- and 1,3-dihydroxy-propane, dihydroxybutanesand dihydroxypentanes. Examples of triols are glycerol,trihydroxybutanes, trihydroxy- pentanes and trimethyolpropane. Examplesof higher alcohols are pentaerythritol, mannitol and sorbitol.

In order to form corresponding succinimide or succinamide derivatives,reaction with an amine which has at least one secondary amine function(NH) or one primary amine function (NH₂), is necessary. Of particularinterest here are linear or branched alkylenepolyamines, cycloaliphaticpolyamines and heterocyclic polyamines, each having 2 to 6 amino groups.Examples of these are ethylenepolyamines, such as ethylenediamine,diethylene-triamine, triethylenetetramine, tetraethylenepentamine orpentaethylenehexamine, propylenepolyamines, dimethylamino-propylamine,α,β-diaminopropanes, α,β-diaminobutanes, di(trimethylene)triamine,butylenepolyamines, piperazine or diaminocyclohexanes.

Of particular interest as derivatives of the novel thermal reactionproducts of maleic anhydride and oligoalkenes are the correspondingalkylsuccinimides which are derived from polyamines having at least oneprimary amine function.

A preferred embodiment comprises those derivatives of the thermalreaction products of maleic anhydride and oligoalkenes with amines inthe form of the corresponding alkenylsuccinimides which are obtainableby condensation of the reaction products of maleic anhydride andoligoalkenes with polyamines, the amount of polyamines used being from10 to 200% above the theoretical amine requirement for the preparationof a bissuccinimide and the amine number of the condensate thus obtainedbeing at least 70% of the theoretical amine number of thebissuccinimide, based on the saponification number of the reactionproduct of maleic anhydride and oligoalkenes.

The maleation of the oligoalkenes (typical conditions: 4 h, 200° C., 10%by weight, based on the oligoalkene, of MAA) is evidently accompanied byother reactions which give products which, after MAA has been distilledoff and the alkenylsuccinic anhydride filtered, do not give any acidnumber or saponification number (SN) but react with the amino groups inthe subsequent imidation stage (typical conditions: 3 h, 180° C.) withpolyamines, with loss of the basicity (amine number).

The theoretical amine number is calculated from the saponificationnumber of the alkenylsuccinic anhydride (SA), assuming an imidationreaction with two moles of anhydride and one mole of polyamine (e.g.tetraethylenepentamine (TEPA)). When using the theoretical amount ofamine, however, the theoretical amine number is not obtained and a poordispersing effect results. The dispersing effect is all the poorer thefurther away the amine number is from the theoretical value. The amountof amine is then increased until at least the theoretical amine numberis reached during the condensation. At this point an excellentdispersing effect is then obtained.

However, a substantially higher amine number should then result for abissuccinimide with the amount of amine then used. By iteration, anamount of amine which corresponds to only three of the originally fiveamine functions after condensation in the case of TEPA is finallyobtained. The optimum effect generally occurs between these two keypoints.

Two examples in Table 1 below are intended to illustrate this unexpecteddiscrepancy between alkenylsuccinic anhydride and amine requirement:

TABLE 1 Calc. amine number for Oligodecenylsuccinic bissuccinimideActual TEPA de- anhydride with 0.5 mol of mand [mol]/ TEPA excess SNtheoretical M_(n) TEPA [mol of SA] [%] 11.25 9,973 8.37 0.85 70 8.014,025 5.96 1.10 120

The novel derivatives of the thermal reaction products of maleicanhydride and oligoalkenes with amines or alcohols are very useful asfuel additives and in particular as lubricant additives, especially asashless dispersants in motor oils. The novel derivatives produceexcellent viscosity/temperature behavior in motor oils to which theyhave been added, so that it is possible substantially or at least partlyto dispense with the conventional viscosity index improvers. Inparticular, a substantial reduction in the low-temperature viscosity isachieved. Moreover, they have an excellent dispersing effect even insmall amounts.

The present invention also relates to motor oils containing from 0.1 to10, in particular from 0.5 to 7, % by weight, based on the motor oil, ofthe novel derivatives of the thermal reaction products of maleicanhydride and oligoalkenes with amines or alcohols. Motor oils are to beunderstood here as meaning both mineral and partly and wholly syntheticmotor oils (based on, for example, mineral oil, synthetic components,such as organic esters, synthetic hydrocarbons, poly-α-olefins orpolyolefins, such as polyisobutene, or mixtures of mineral oil with suchsynthetic components). Such motor oils can be used for a very wide rangeof intended applications (for example, four-cycle motor oils, two-cyclemotor oils, automobile and motorcycle motor oils, marine diesel engineoils, locomotive diesel engine oils, etc.). The novel derivatives of thethermal reaction products are also suitable as additives in gear oils.

In the examples which follow and illustrate the invention withoutrestricting it, percentages are by weight, unless stated otherwise.

PREPARATION EXAMPLES Example 1

Synthesis of an oligodecene with {overscore (M)}_(n)=11,400

In a 1 l stirred autoclave having a V4A stainless steel double jacket,400 ml of linear 1-decene (polymer quality, 99.8%) were initially takentogether with 300 ml of ethylbenzene dried over Al₂O₃ and were heated to50° C. 44 mg of (ethylidenebis-indenyl)zirconium dichloride weredissolved in 43.8 ml of methylaluminoxane (10% strength in n-hexane) ina Schlenk vessel, forced into the reactor through a lock a little at atime by means of nitrogen and washed through with 30 ml of ethylbenzene.The portions were such that the cryostat which removed the heat ofreaction was not overloaded and could keep the reaction temperature at50° C. The maximum difference in temperature between jacket and reactorcontent was 40° C. which disappeared in the course of from 2 to 3 hours.After 4 hours, the mixture was cooled to room temperature, and theautoclave was emptied and dilution was effected with aliquot amounts ofcyclohexane. Washing was carried out with 100 ml of 0.1% strengthsulfuric acid and with twice 100 ml of demineralized water, drying wascarried out over Na₂SO₄ and distillation was effected up to 225° C. (2mbar). The bottom product had a viscosity of 1100 mm²/s (100° C.) and an{overscore (M)}_(n) of 11,400 according to GPC. The yield was 85% andthe vinylidene double bond content was 94%.

Example 2

Reaction of the oligodecene from Example 1 with maleic anhydride (MAA)and derivatization with tetraethylenepentamine (TEPA)

200 g of the oligodecene from Example 1 were initially taken with 20 gof MAA in a 0.5 1 V2A stainless steel stirred autoclave, evacuated to 20mbar, brought to atmospheric pressure with nitrogen and evacuated againto 20 mbar. The mixture was then heated to 200° C. and kept at thistemperature for four hours, after which the autoclave was let down andthe mixture was freed from excess MAA at 2 mbar. The reaction producthad a saponification number of 6.0. After the temperature had beenreduced to 180° C., 1.53 g of TEPA were added and condensation wascarried out for a further 2 hours. The acid number of the imide was 0.7and the amine number was 4.8.

Example 3

Synthesis of an oligodecene with {overscore (M)}_(n)=5600

400 ml of linear 1-decene (purity: 96%) and 300 ml of ethyl-benzenedried over Al₂O₃ were initially taken in a 1 l stirred autoclave havinga double jacket according to Example 1 and were cooled to zero ° C. 80mg of bis(n-octadecylcyclopentadienyl)-zirconium dichloride wereactivated with 32 ml of methylaluminoxane (10% strength in n-hexane) ina Schlenk vessel and were added in two portions in the course of 5minutes. A temporary temperature increase from 2 to 3° C. was observed.After 8 hours at 0° C., the reactor was emptied, the reaction wasstopped by slow dropwise addition of dilute sulfuric acid whilestirring, and working up was effected as in Example 1. An oligodecenehaving a viscosity of 580 mm^(2/)s at 100° C. and an {overscore (M)}_(n)of 5600 according to GPC was obtained. The yield was 83% and thevinylidene double bond content was 95%.

COMPARATIVE EXAMPLE A:

Derivative of polyisobutenylsuccinic anhydride (PIBSA) with TEPA

For comparison, 200 g of highly reactive polyisobutene having a numberaverage molecular weight ({overscore (M)}_(N)) of 2330 and a vinylidenedouble bond content of 77% were initially taken in a V2A stainless steelstirred autoclave, heated to 160° C., evacuated, and stripped withnitrogen. 13 g of MAA in liquid form were metered in while stirring inthe course of 1 hour. The temperature was then increased to 225° C. andthe reaction was allowed to continue for 4 hours. Excess MAA was removedunder a reduced pressure of 2 mbar. The reaction product had asaponification number of 42. After the temperature had been reduced to180° C., TEPA was added in a ratio to PIBSA of 1:2, i.e. 7.9 g, andcondensation was carried out for a further 2 hours.

Testing the viscosity/temperature behavior

The products from Example 2 and Comparative Example A were tested asashless dispersants in a concentration of 6% in a 5w/30 motor oil havingthe following composition:

conventional poly-α-olefin 54.4 or 48.4% (viscosity: 6 mm²/s)conventional poly-α-olefin 20% (viscosity: 4 mm²/s) diisononyl adipate20% ashless dispersant 0 or 6% conventional superbasic sulfonate 3% zincdithiophosphate 1.8% conventional antioxidant 0.5% conventional frictionmodifier 0.2% conventional antifoam 0.1%

The results are summarized in Table 2:

TABLE 2 Dispersant Viscosity at Viscosity at according to 100° C. −25°C. example [mm²/s] [mPa s] Solubility no dispersant 7.55 1900 clear 212.15 3000 clear A 10.85 3400 clear

The novel dispersant from Example 2 is accordingly substantiallysuperior to the prior art (Comparative Example A) owing to the greaterviscosity-increasing effect at high temperature in combination withlower viscosity at low temperature.

Testing of the dispersing effect

For testing the dispersing effect, the spot test was carried out(described in “Les Huiles pour Moteurs et la Graissage des Moteurs”, A.Schilling, Vol. 1, page 89 et seq., 1962). For this purpose, 3% strengthmixtures of the dispersants in a particulate diesel oil were prepared.The dispersions thus obtained were developed on a filter paper in thesame way as a chromatogram. The rating scale extended from 0 to 1000:the higher the value obtained the better the dispersing effect.

The results are summarized in Table 3.

TABLE 3 10 min at 10 min at Dispersant 20° C. 10 min at 250 ° C. 10 minat according to without 20° C. without 250° C. example water with waterwater with water 2 (with 3% of 675 677 704 701 dispersant) 2 (with 2% of654 638 654 638 dispersant) A (with 3% of 651 647 643 661 dispersant)

The novel dispersant from Example 2 had a significantly betterdispersing effect than the prior art in all cases, since 2% of theproduct from Example 2 are sufficient to achieve a dispersing effectcomparable with that achieved with 3% of Comparative Example A.

We claim:
 1. A thermal reaction product of maleic anhydride andoligoalkenes which are obtainable by metallocene-catalyzedoligomerization of linear 1-decene, it being possible for up to 40%,based on the amount of linear 1-decene, of further linearC₈-C₁₂-1-alkenes to be incorporated as polymerized units in the presenceof a titanium, zirconium or hafnium metallocene catalyst and of anactivator based on organoaluminum, organoboron or carbocationiccompounds, have a vinylidene double bond content of more than 30% andhave a number average molecular weight of from 700 to 20,000.
 2. Athermal reaction product as claimed in claim 1 of oligoalkenes which areobtainable by oligomerization of 1-alkenes which are used virtually freeof more highly volatile hydrocarbons of less than 8 carbon atoms.
 3. Athermal reaction product as claimed in claim 1 of oligoalkenes having anumber average molecular weight of from 2000 to 15,000.
 4. A derivativeof a thermal reaction product of maleic anhydride and oligoalkenes asclaimed in claim 1 with amines or alcohols in the form of thecorresponding alkenylsuccinamides, alkenylsuccinimides oralkenylsuccinic esters.
 5. A derivative of a thermal reaction product ofa maleic anhydride and oligoalkenes with amines in the form of thecorresponding alkenylsuccinimides as claimed in claim 4, obtainable bycondensation of a reaction product of maleic anhydride and oligoalkeneswith polyamines, the amount of polyamines used being from 10 to 200%above the theoretical amine requirement for the preparation of abissuccinimide and the amine number of the condensate thus obtainedbeing at least 70%, based on the saponification number of the reactionproduct of maleic anhydride and oligoalkenes, of the theoretical aminenumber of the bissuccinimide.
 6. A motor oil containing from 0.1 to 10%by weight, based on the motor oil, of derivatives of the thermalreaction products of maleic anhydride and oligoalkenes with amines oralcohol as claimed in claim
 4. 7. A process for preparing thermalreaction products by heating maleic anhydride with oligoalkenes obtainedby oligomerization of linear C₈- to C₁₂-1-alkenes, have a vinylidenedouble bond content of more than 30% and have a number average molecularweight of from 700 to 20,000, in the absence of compounds initiatingfree radical chain reactions, at temperatures of from 150 to 250° C.,wherein the oligoalkenes have been obtained by metallocene-catalyzedoligomerization in the presence of a titanium, zirconium or hafniummetallocene catalyst and of an activator based on organoaluminum,organoboron or carbocationic compounds.
 8. A process for preparingderivatives of the thermal reaction products of maleic anhydride andoligoalkenes, as set forth in claim 7, which comprises reacting thethermal reaction products with amines or alcohols to give thecorresponding alkenyisuccinamides, alkenylsuccinimides oralkenylsuccinic esters.